The present invention provides vinyl esters containing a polymeric domain containing mesogenic or rigid rodlike moieties, polymerizable mixtures thereof with one or more ethylenically unsaturated monomers and cured compositions prepared from either the vinyl ester containing a polymeric domain containing mesogenic or rigid rodlike moieties or the vinyl ester and polymerizable monomer mixture. The precursor to said vinyl ester is an epoxy resin containing a polymeric domain containing mesogenic or rigid rodlike moieties. The present invention also provides cured compositions prepared from mixtures of the epoxy resin containing a polymeric domain containing mesogenic or rigid rodlike moieties and one or more curing agents and/or curing catalysts therefor. A wide variety of mesogenic (anisotropic) or rigid rodlike containing monomers and their respective polymers are well known. Representative of these monomers and polymers are those referenced by Alexandre Blumstein Liquid Crystalline Order in Polymers published by Academic Press, New York (1978) on pages 105-140: Alexandre Blumstein in Mesomorphic Order in Polymers and Polymerization in Liquid Crystalline Media published by American Chemical Society (ACS Symposium Series 74), Washington, D.C. (1978) on pages 56-70: and N. A. Plate and V. P. Shibaev in Comb-Shaped Polymers and Liquid Crystals published by Plenum Press, New York (1987) on pages 1-415. All of the aforementioned references are incorporated herein by reference.
Blends of polystyrene containing up to 10 percent of a liquid crystalline polymer are described by R. A. Weiss, et. al. in Polymer Engineering and Science, Mid-May, volume 27, number 9, pages 684-691 (1987). Benefits imparted by the immiscible liquid crystalline polymer additive include reduced viscosity in the direction of flow during processing and increased tensile modulus in the thermoplastic product. A. Apicella, et. al. in Polymer Engineering and Science, Mid-May, volume 26, number 9 (1986) characterized extruded then hot drawn blends of polystyrene with non-compatible polymeric liquid crystals. Improved dimensional stability in the thermoplastic was observed. Numerous other blends of thermoplastics with liquid crystalline polymers have been prepared and characterized including, for example liquid crystal polymer blends with polycarbonate (A. I. Isayev and M. J. Modic, Antec 86. Plastics--Value Through Technology. Proceedings of the 44th Annual Technical Conference, Boston, pages 573-579, Apr. 28 -May 1, 1986): with polyethylene terephthalate (E. Joseph, et. al., Polymer Preprints, volume 25, number 2, pages 94-95, August, 1984: and with nylon 66 (K. G. Blizard and D. G. Baird, Antec 86. Plastics--Value through Technology. Proceedings of the 44th Annual Technical Conference, Boston, pages 311-315, Apr. 28-May 1, 1986).
Vinyl esters are the reaction product of about equivalent amounts of a monounsaturated monocarboxylic acid and a polyepoxide. One class of vinyl esters is described by Bearden in U.S. Pat. No. 3,367,992 where dicarboxylic acid half esters of hydroxyalkyl acrylates or methacrylates are reacted with polyepoxide resins. Bowen in U.S. Pat. Nos. 3,066,112 and 3,179,623 describes the preparation of vinyl esters from monocarboxylic acids such as acrylic or methacrylic acid. Bowen also describes alternate methods of preparation wherein a glycidyl methacrylate or acrylate is reacted with the sodium salt of a dihydric phenol such as bisphenol A. Vinyl ester resins based on epoxy novolac resins are described in U.S. Pat. No. 3,301,743 to Fekete, et. al. Fekete, et. al. describe vinyl esters where the molecular weight of the polyepoxide is increased by reacting a dicarboxylic acid with the polyepoxide resin as well as acrylic acid, etc. in U.S. Pat. No. 3,256,226. Najvar describes rubber modified vinyl esters in U.S. Pat. No. 3,892,819. Other functional compounds containing a group reactive with an epoxide group, such as an amine, mercaptan and the like, can be utilized in place of the dicarboxylic acid. All of the above described compositions, which contain the characteristic linkages ##STR1## and terminal vinylidene groups are classified as vinyl esters and are included herein by reference. The vinyl esters thus prepared are typically combined with a reactive diluent, a copolymerizable vinyl monomer, to alter the viscosity of the mixture, to vary properties of the cured resin, or for other known reasons. Both the vinyl ester and the vinyl ester blend with a copolymerizable vinyl monomer are curable (thermosettable), typically by mixing in a free radical forming catalyst and applying heat and/or adding an accelerator.
In the present invention the polymeric domains containing mesogenic or rigid rodlike moieties impart improved mechanical properties, notably tensile and flexural strength plus tensile elongation, to the cured (thermoset) vinyl ester resin. In the cured epoxy resin, the polymeric domains containing mesogenic or rigid rodlike moieties impart increased Gardner impact strength as a film coating. Furthermore, the creation of a specific polymeric domain containing mesogenic or rigid rodlike moieties in the polyepoxide precursor to the vinyl ester resins serves to efficiently disperse polymeric material containing mesogenic or rigid rodlike moieties into either the vinyl ester resin or epoxy resin. By way of contrast, attempts to disperse, blend or dissolve polymeric materials containing mesogenic or rigid rodlike moieties directly into the vinyl ester resin leads to liquid resin containing large aggregates of particulate polymer which subsequently exert a deleterious effect on mechanical properties of the thermoset resin, i.e., by serving as a flaw site for induction of mechanical property failure. At elevated temperatures (100.degree. C. and above) only minor amounts of polymeric materials containing mesogenic or rigid rodlike moieties are solubilized into the vinyl ester resins. Curing at these elevated temperatures invariably leads to crazed and/or cracked castings of poor mechanical strength due to the exothermic nature of the cure process. Reduction of the cure temperatures leads to phase out and aggregation of all or a part of the polymeric material containing mesogenic or rigid rodlike moieties. The invention consists of the (A) epoxy resins containing a polymeric domain containing mesogenic or rigid rodlike moieties: (B) mixtures of said epoxy resins or said epoxy resins admixed with one or more polymeric materials containing mesogenic or rigid rodlike moieties; (C) epoxy resins containing a polymeric domain containing mesogenic or rigid rodlike moieties or mixtures of said epoxy resins or said epoxy resins admixed with one or more polymeric materials containing mesogenic or rigid rodlike moieties admixed with one or more curing agents and/or curing catalysts therefor, whether or not cured; (D) vinyl esters containing a polymeric domain containing mesogenic or rigid rodlike moieties: (E) mixtures of said vinyl esters with one or more polymerizable ethylenically unsaturated monomers: and (F) mixtures of said vinyl esters or said vinyl esters admixed with one or more polymerizable ethylenically unsaturated monomers with one or more polymeric materials containing mesogenic or rigid rodlike moieties, whether or not cured.